A vane-type vacuum pump has been used in a vehicle such as a car in order to, for example, cause a negative pressure chamber of a brake booster to be in a negative pressure. Examples of such vacuum pumps include those shown in PTLs 1 to 4. Pumps shown in PTL 1 and PTL 2 have such a structure that main members such as a cam ring (cylinder) accommodating a roller in an inner peripheral side hollow portion, a plate (main bearing) for sealing one of opening portions of the cam ring and a plate (sub bearing) and the like for sealing the other of opening portions of the cam ring are disposed in a case.
In a pump as shown in PTL 3, a ditch-shaped groove portion is provided between an inner periphery and an outer periphery of a center case accommodating a rotor in an inner peripheral side hollow portion. The opening portion of the groove portion is sealed with the side cover, so that a sealed chamber is formed. In this case, the sealed chamber is used as a diffusion chamber of a muffler.
In a pump as shown in PTL 4, a feature of forming a casing main body using a material of a high degree of thermal conductivity can be disclosed.